Delivery of therapeutic agents to the spinal cord, such as sustained release preparations of small molecules or peptides, vectors for gene therapy, or cellular transplants to the spinal cord require injection of the spinal cord parenchyma. Penetration of the spinal cord and deployment of a cannula over the time required for injection poses the risk of sheering the axonal tracts of the spinal cord. To avoid this risk, the cannula can be fixed with respect to the spine of the patient to prevent the cannula from shifting during injection. The spinal cord moves with respiration and cardiac rhythm, however, and these movements pose a further risk to the spinal cord during prolonged injection.